I think the pegs that hold joints together need to be the strongest wood you can get. That probably means oak.
Power required depends partially on the wood you are drilling. Pine can be worked with a more modest drill than you would need for oak.
I haven't seen instructions, but I did recently see a
youtube video with a brace jig and matching mortise locating template. Essentially they had a three sided box (with adjustable length?) whose ends were at 45 degree angles, to put a brace blank in and guide the tenon cutting.
The video shows what they consider an appropriate length for braces; I think you can get a good idea from that.